Patent GB-292498-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1928-04-28
Abstract: 292,498. Associated Telephone & Telegraph Co., (Assignees of Ruggles, L. L.). June 20, 1927, [Convention date]. Automatic and semi-automatic exchange, time controlling, and party-line systems. -In a small magneto office in which the establishment of connections is controlled by an operator at a distant office, a call is initiated by momentary application of ringing current to the line whereupon a plunger type line switch connects the line to a connector, and a relay chain acting like a call finder connects the operating trunk from the distant office to the connector. If the call is a reverting one, the operator sets the connecter to a special position in which circuit changes take place whereby the Tinging code, selected by a further switch, is sent back over the incoming leads. In all cases the ringing code is sent only once. The switches are released when used for local calls by a further application of ringing current to the line. If not so released, they an released automatically a predetermined time after the connection is set up, or, if the operating trunk fails to find the calling connector, a predetermined time after it is seized. When used for inter-office calls, the switches are released automatically when the connection is taken down at the main office. When all the connectors are off-normal, the operator receives a call signal over the operating trunk and on listening hears a busy tone. She then takes into use one of a pair of two way junctions terminating at the magneto office in connectors and sets the. connector to a particular level in which each set of terminals is associated with a particular local connector. She can thus listen in to each connector and releases any that are not in use. If a fault occurs, a call signal and a characteristic tone are given over the operating trunk and the operator then sets one of the junction connectors to a particular level and then over the level one step at a time. In a position characteristic of the particular fault she hears a tone signal. Means a,re provided for enabling either of the junctions to be used as the operating trunk, the necessary circuit changes at the magneto office being controlled from the other office by setting the associated junction connector to a particular position. Conditions are restored to normal by setting the other junction connector or one of the local connectors to another particular position. In case all the lines between the offices are destroyed an operator can make use of an emergency set at the magneto office for controlling the selectors. Every time a call is made the battery is connected to a charging source and is automatically disconnected when full. Line switch and master switch. Before removing his handset, the subscriber operates his generator to operate relays 302, 301 and the pulldown winding 303 of his line switch. The cut-off winding 304 then holds the switch, relays 302, 301 are released, and relays 306, 307 pull up. The master switch test relay 342 which is energized alternately over the plunger contact 377 or over a contact of the off-normal relay 306 causes the master switch to move on unless all the other connectors are busy or off-normal, in which case a chain circuit is completed for a disabling relay 341. Busy signal and release. Busy relay 315 conmon starting wire 221 whereupon relay 205 connects interrupter 217 to a counting chain of the two-relays-per-impulse kind. The counting relays successively connect the stop relay 201 to the marking wires such as 222, the connectors being tested in the same order as by the master switch and when the calling connector is found, 201 energizes 309, to complete a talking circuit to the operating trunk, and connects 202 to the trunk. Relay 202 pulls up over both legs in parallel, in series with 101, which gives a lamp signal to the operator, and is followed by 203, 204. Control of connector by operator. The operator now operates the right hand springs of key 104 to answer the call, replacing 101 by dial springs CD1 and energizing 103, 102 to light a busy lamp. Relay 202 repeats the first two digits to the vertical and rotary magnets 326, 327. Relay 308 which is operated alternatively by the series relay and off-normal springs locks itself and makes the connector non-selectable to the finder. Busy signal and release. Busy relay 315 connects up busy tone which is heard by the calling party and the operator who then dissociates the operating trunk from the connector, causing the operation of relay 313 which releases the connector. These operations are described in detail below. Party-line code ringing. Switching relay 317 on the relapse of the rotary dialling relay 316, extends the impulse circuit to the magnet 409 of a switch CS1 which, in response to a further digit, selects a particular code produced by a constantly rotating switch CG. Relay 405 is energized while the switch CS1 is off normal and at the end of the digit, the relapse of relav 406 connects the pickup relay 407 to wiper PU of the code switch. At. the beginning of the next cycle 407 completes the ringing circuit over the selected code wire. The code which is only sent once, consists of a long warning ring and a series of short rings. At the end of the code, the switch CG energizes the ring- ing cut-off relay 318, the release magnet 410 and the relay 408 which holds the release magnet until the switch CS1 reaches normal. Relay 318 cuts off 309 in case the operator has not already done so and completes the talking circuit. The code selecting switches associated with the junction connectors differ slightly from the switch CS1 and are described in a later paragraph. Release. Relay 320 which is short circuited by relay 319 while the connection is being set up, is bridged across the talking wires when relay 318 pulls up. The short circuit is maintained for a short interval governed by the release time of 319 to allow the lines and substation condensers (if any) to discharge. At the end of the conversation, relay 320 is operated by the substation generator of either party and relays 311, 312 pull up. When the generator stops relays 311, 312 fall back sluggishly in succession making a momentary circuit for 313 which releases the line switch and relay 307 then falls back. The relapse of 307 energizes the release magnet 321. Dissociation of operating trunk from connector. On hearing the ring-back or busy time, the operator temporarily throws key 104 to operate its left hand springs. Relays 103, 102 and relays 202, 203, 201 205 and the operated chain relays fall back, followed by 309. If there is a waiting call, 205 remains up and the chain at once begins to build up from the point at which it stopped. If, owing to a fault, 308 has failed to operate, 201 is prevented from re-operating by relay 204 which holds up long enough for the chain to take another step. The chain thus runs through a complete cycle before again stopping on the faulty connector and may stop on an actual call on the way. Reverting calls. The connector is set to a special position in which springs 324 change over to operate 310 which arranges for the ringing code to go back over the incoming leads and subsequently causes 313 to operate in parallel with 318 at the end of the code to release the switches. The latter provision which leaves the line unguarded may be disabled by omitting the jumper 379. Calls to neighbouring office. The connector is set to whichever of the junctions TT1, TT2. is idle and the operating trunk is disconnected. The relapse of 309 energizes 318 over shaft springs 323 operated on this level. Relay 501, which is energized over the test wiper, connects alternating current to the junction and is cut off shortly afterwards by the second of two sluggish relays which it causes to pull up in succession. This relay, 503, locks itself and energizes 505 to switch over the junction from the associated connector to the local connector. At the main office end, 115 responds to the alternating current, locks up and lights calling lamps at the local and toll boards. The toll operator plugs in and 113 pulls up sluggishly and energizes 114 which releases 115. The calling lamps go out and busy lamps are lit. Relay 112 is energized over both junction wires in parallel, in series with 514 which energizes 515. At the end of the conversation, the toll operator withdraws the plug and relays 113, 114, 112, 514, 515 fall back. In the interval between the relapse of the two last-mentioned relays a circuit is made for 504 which connects battery and ground for an instant to the talking wires to operate and release relay 320 and so release the line switch and connector. This releasing impulse is prevented from passing to the calling line by a condenser which is inserted in the upper talking wire by shaft springs 322 in outgoing calls. Calls to remote office; incoming calls The toll operator on receiving a call for a remote office tells the subscriber to hang up and removes the plug to release the local connector. After getting the wanted connection she plugs into one of the junctions. In this case, 112 is energized in series with 506 which energizes 507 to busy the junction to local connectors. The operator then replaces 112 by the dial springs CD2 by means of a dialling key 117, sets the incoming connector TC1 to the calling party's line and operates the associated code-selecting switch CS2. The ringing code is sent out in the manner described above except that the stop relay 609 itself cuts off the ringing leads and the code selecting switch is not released until the end of the connection. Relay 509 is energized at the same time as 609 and completes the talking circuit. When the connection is taken down, 506, 507 fall back and release the connector. Incoming calls are set up in the same way. Timed release of line-switch and connector. Relay 307 which pulls